Many Iowa soybean producers have adopted Roundup Ready (RR) technology on their farms in recent years. Reduced weed control costs, greater flexibility in herbicide application timing, and the potential for “cleaner” soybean fields are often cited as reasons for using RR technology; however, questions remain about potential profit-robbing yield reductions associated with RR varieties. A soybean yield performance comparison of adapted, elite RR varieties and elite conventional varieties was initiated in 1999. Our research objective was to compare the genetic yield potential of commercial varieties, not to analyze the economics of one soybean variety-herbicide program versus another. Establishment of similar studies at four other university research farms statewide afforded yield response comparisons of adapted varieties from five unique soil associations and environments. Soils at the Northwest Research and Demonstration Farm are typical of the Galva-Primghar soil association.